1. Field of the Invention
The present invention relates to an integrated circuit driver, and more particularly, to an integrated circuit driver with on-chip termination.
2. Description of the Related Art
In designing integrated circuits (IC) that process digital signals or data, circuit designers must account for losses or degradation of signals due to intended or unintended simultaneous operations among peripheral circuits and devices, such as signal distortion, signal reflection or power consumption. Data communications between integrated circuits or peripheral circuits can be degraded due to load capacitance and impedance mismatch that exist in transmission lines. Typically, matching devices or circuits are used for matching the impedance between internal circuits and external circuits, particularly for driver circuits which outputs signals or data from one IC to another IC chip. In general, a termination circuit for matching characteristic impedance and controlling electrical load are provided in order to prevent signal reflection or line reflection from occurring in transmission lines to which output circuits and peripheral circuits are connected. Resistors are typically used as a termination device. By connecting resistors to the transmission line, the characteristic impedance of the transmission line can be matched and the signal reflection and discontinuity problem can be attenuated.
Integrated circuits having on-chip termination devices are known. In designing interfaces requiring on-chip termination, terminals (or input/output ports) should include both a driver and an on-chip termination circuit for bi-directional (input and output) signal transmissions. However, since such design construction result in an increase of circuit area and load capacitance of the interface structure, there is a need to include the on-chip termination within the driver. Further, since the impedance of input and output devices of an integrated circuit and external transmission line is sensitive and can vary due to process, voltage or temperature variations, there is a need for efficient and flexible impedance control based on desired impedance states.